Your problem most likely lies in Codecs. A Codec is a piece of software that allows your media players and audio/video programs to use certain formats. Every single format that exists requires a certain Codec for programs to communicate with it. An amigo somewhere above me mentioned a good Codec pack, and you could also try the K-Lite Codec pack as well. As for using Media Player 9, you really should try newer ones but you do not have to. The newer ones have more Codecs already loaded [so you don't have to spend time getting them yourself] but nonetheless MP9 can play anything that MP11 can, provided you get the right Codecs. And finally, I really recommend VLC Media Player, which plays almost anything right out of the box. Different versions have been made for Windows, MacOS and Linux Operating Systems it doesn't use very much system resources [RAM, CPU usage, etc] Well, I hope that Solves your problems amigo.